docs: def add_input(self, name, value=None):
          '''Create a new input variable called ``name`` for this process
          and initialize it with the given ``value``.
  
          Quantity is accessible in two ways:
  
              * as a process attribute, i.e. ``proc.name``
              * as a member of the input dictionary,
                i.e. ``proc.input['name']``
  
          Use attribute method to set values, e.g.
          ```proc.name = value ```
  
          :param str name:        name of diagnostic quantity to be initialized
          :param array value:     initial value for quantity [default: None]
          '''
          self._input_vars.append(name)
          self.__setattr__(name, value)